DUBAI:  Iran and the United States continue to exchange messages through Pakistan, a senior Iranian source told Reuters on Tuesday, but Tehran will not show flexibility as long as Washington continues to demand its "surrender under pressure".

The senior Iranian source, who asked not to be named, said Qatar on Monday had conveyed Tehran's message to the United States and regional countries that if Washington attacks Iran's power plants, "the entire region and Saudi Arabia will fall into complete darkness with Iran's retaliatory strikes".

He also warned that "if the situation gets out of control, Iran’s allies will also close the Bab El-Mandeb Strait".